Work is being carried out on regulation of pancreatic acinar cell function by insulin. Isolated pancreatic acini are prepared from rats made diabetic with streptozotocin to reduce endogenous insulin levels. We have characterized insulin binding sites on these acini using 125I-insulin. We are presently studying the cellular localization and internalization of insulin by acini by use of electron microscopic autoradiography. Insulin in physiologic concentrations stimulates protein synthesis in acini and we are characterizing this phenomenon examining both incorporation of amino acid into total protein and into specific digestive enzymes isolated by immunoprecipitation. Studies are also underway characterizing the mechanism of insulin degradation by isolated pancreatic acini.